Synchronizing arrangment



March 12,1935. E, s, PURlNGTON 1,994,230

SYNCHRONI Z ING ARRANGEMENT Filed Oct. 20, 1928 2 I BY im; 5gg/MM RNEY yPatented Mar. 12, 1935 PATENT OFFICE SYNCHRONIZIN G ABRANGMIENT Ellison S. Purlngton, Gloucester, Mass., assiznor to John Hays Hammond, Jr.

Application October 20, i923, Serial No. lilfl'll fl laims.

One of the objects of this invention is to provide a method of controllingt a rotating shaft in accordance with periodic changes oi an electric current.

Another object is to provide a quick; acting electrical brake whereby the braking torque on a rotating deviceI may be changed hy the application of a small amount of electrical power.

A further object is to control the output of a mechanical type alternating current generator to be in electrical synchronism with an electrical oscillation.

A still further object is to provide a smooth and steady motion tor driving moving .parts oi mechanical and electrical devices.

Other objects will become apparent from the following description taken in connection with the accompanying drawing. In. the particular application shown in this specification for the purpose of illustration, the controlling current is derived from a vacuum tube oscillator, and it is desired that the rotating shaft rotate in an ex tremely smooth and constant manner in order to provide the driving mechanism for picture transmission and reception, television synchronization andsimilar uses. In this application, similar driving mechanisms may be used at the transmit- .ter and at the receiver, with slight adjustments at the receiver such that slight corrections may be made from time to time oy manual control, if required.

The following elements are required to cornvprise the apparatus ci my invention,

1 A controlling device. This serves to deter= mine and control the speed o mechanical motion. In practice it may be a vacuum tube oscillator system comprising con-densers and coils arranged in the usual and well known manner.

It may comprise tuning forks and other electrodynamical devices. The controlling device may f be at a distance, and the control may operate through use of a transmission line or a radio channel, A simple key circuit for throwing dlrect voltage into a control circuit may be the control device, by manual operation, out the chief applications will involve automatic control from a periodically varying electrical source. It is to be understood, however, that the nature of the source of electric oscillations to be the controlling element of the mechanical rotation is not limited to those named, but may be any source of constant frequency electric variations, It is understood also that any well known and readily constructible means may he provided for (Cl. H2B-293) varying the :frequency of the oscillating current ior purposes of adjustment.

2. .im alternating current generator ot the mechanical type, with suitable motive power for driving, such as an A. C. or D. C. motor, air turbines, spring motor, etc. The type ci drive for the generator is not limited in this invention, nor is the type ci generator used limited. It is merely required that the generator periodicity correspond to a mechanical speed of motion. It is understood that the motor may loe further used to operate other devices, such as a scanning diei: used in television transmission. It is further understood that the mechanical type A. C. cenerator may he used to drive electricaldevices other than the electrical discharge system.

3. An electrical discharge system with accomcarrying circuits adapted to be energized trom the il. C. mechanical type generator, and also with circuits adapted to loe energized by the con trol device, such that the power drawn from the mechanical type generator may he varied. This discharge system may loe based on the use ci the three electrode vacuum tube of the usual type.

Having lorie y described my invention, attention is invited to the accompanying' drawing', wherein,

Fig. represents a general layout oi a system constructed accordance with my invention; n

and,

Fig. 2 is a diagram showing the relationship between grid and plate voltages, and plate current, at varying phase displacements.

Figure 3 represents a general layout of a systern constructed in accordance with the invention in which the prime mover is shown gener ally and the control is obtained by the load char acteristics ci the electronic system.

Having thus briedy described the drawing, attention is now particularly invited to Fig. l, wherein the controlling device is an alternating current source which is to be matched in periodicity by a corresponding mechanical rotation. This source is a vacuum tube oscillating circuit arranged in a well known manner as shown al; il. Special care should be taken in design so that the oscillations produced by this generator are of a very constant frequency, inde endcnt of slight chartres oi plate and grid voltages, tem perature, and loading'. Further this may he arranged so to provide manual control ci the frequency ior adjustment purposes by varying the capacity o the condenser or the controilina1 inductance such as oy means oi a variorneter.

desired the frequency of this circuit may he au- Lartistically controlled sans un mana suchasapendulumclock. lurthermoreacrystalmaybeusedtocontrolthefrequeneyofthne oscillatortoaverygreatdegreeofaccuracy. The mechanical type A. C. generator is shown at 12, and this is adapted-to be driven by a D. C.

, motor shown at 13. The generator may be a multiple pole machine, for example, with 8 cycles per revolution, in which case the frequency gen-- a television transmitter or receiver.

Comprising the electrical discharge system there is shown, at 14, in this instance. a pushpull vacuum tube circuit comprising the thermionic devices -15 and 18, the filaments of which -areadaptedtobesuppliedbythebatteryl'lin the usualy and well known mannenand at 11 a vacuum tube oscillator inductively coupled into the grid circuits of the push-pull vacuum tubes. The output of the A. C. generator 12 is coupled to the plate circuit of the push-pull circuit 14. For making these couplings, any suitable transformers may be used. A suitable bias battery may be used in the grid circuit of the push-pull The plate circuit is the circuit between the filaments and the center tap of the plate circuit transformenas in the usual rectifier connection. In the present case, this circuit includes the D. C. meter 18 and the field winding 19 of motor 13. The use of a eld winding is not essential to the invention since it is applicable only to D. C. mo-

tor drivel while the invention is applicable to all types of motor drive. It is in some cases most satisfactory to operate with only the indicating meter, 18, in the output circuit connected between center tap of the transformer and the filaments, in which case the power rating of the vbrake is limited by heating of the tubes. Por better design, an ohmic resistance such as a set of lamps in series may be connected in the output circuit, which will permit greatly increased power at higher voltage to be taken from the generator without exceeding the proper tube losses.

Operation of this system depends upon the fact that the loading of the A. C. generator changes with a change of relative phases of the voltages impressed into the plate circuits and grid circuits of the loading tubes.

In Figure 3 an alternating current source ll is shown coupled to the input of a push-pull circuit including two thermionic devices 15 and 18. 4I'he output 14 of the push-pull arrangement is coupled to the output of generator 12 in the same manner as shown in Figure 1. Generator 12 is driven by a primemover 20. The prime mover 20 may be of any conventional type, such for instance, as a steam engine or turbine, alternating current motor, air turbine and the like. Leads 21 and 22 are connected to any suitable current source to provide the necessary ileld for generator 12 in the customary manner. The operation of 'the device shown in Figure 3 depends entirely upon the fact that the loading of the aim cm'rentgeneratorisati'ectedwithachangeof relativephaseofthevoltagesintothe plate circuits and grid circuits ofthe loading push-pull arrangement.

TheFlg.2 isanoperationaldiagramillustratingtheactionofthetube 15,forinstance,inthe simplecasewithno impedanceintheplatecircuitexternaltothe tube. Therepresent grid voltage and the ordinates represent plate voltage. The characteristics of the tube with respect to plate current are indicated by the -the form of said line of operation dependingupon the relative phases of the oscillations in the plate and grid circuits.- The co instantaneous value of the plate current will be that indicated by the lines of instantaneous plata current at any given instant depending upon the position of operation in the line of operation ofthe plateandgridvoltageatanygiveninstantl and the average plate current will be the sum of the instantaneous plate currents. Thus, if the plate applied voltage is out of phase with respect to the grid applied voltage so that the instantaneous plate voltage is maximum when the instantaneous grid voltage is minimum, point A on the diagram, then the average plate impedance is high with little or no power drawn through the generator. This corresponds with the line of operation AB of'Flg. 2. However, if.

the generator gains a half cycle over the control current so that the plate and grid are simultaneouslyamaximumwithzerodegreesphasedifference, the average plate impedance is lowand large power is drawn through the generator. This corresponds with the line of operation CD with the peak current at D exceeding 200 milliamperes. Intermediate phases are represented by elliptical lines oi operation and correspond to intermediate values of loading. The magnitude of loading or braking torque is indicatedby the D. C. meter 18.

Stability of operation requires that the range of controlling torque due to the vacuum tube circuits must exceed fluctuations of mechanical driving torque of the motor and of mechanical loading torque due to driven devices other than the generator. In operation the motor drive is adjusted by means of rheoatats until the generator frequency and controlling frequency match, with the meter indicating no beat action. Subsequently if there is any tendency of the generator to speed up due to more torque being applied from the motor, or less torque required by driven devices other than the generator. or less loading on the generator due to other circuits than the control circuit, then the co phase shift of the plate voltage with respect to the grid voltage produces an additional braking torque which establishes equilibrium again with but slight permanent phase shift. Similarly any torque action tending to slow down the generator will be compensated forvby a weakening of the braking tOlQuG- 

